Without limiting the scope of the invention, its background is described in connection with thermal inkjet printers, as an example.
Modern printing relies heavily on inkjet printing techniques. The term “inkjet” as utilized herein is intended to include all drop-on-demand or continuous inkjet printer systems including, but not limited to, thermal ink-jet, piezoelectric, and continuous, all of which are well known in the printing industry. Essentially, an inkjet printer produces images on a receiver medium, such as paper, by ejecting ink droplets onto the receiver medium in an image-wise fashion. The advantages of non-impact, low-noise, low-energy use, and low cost operation, in addition to the capability of the printer to print on plain paper, are largely responsible for the wide acceptance of inkjet printers in the marketplace. The printhead is the device that is most commonly used to direct the ink droplets onto the receiver medium. A printhead typically includes an ink reservoir and channels, which carry the ink from the reservoir to one or more nozzles.
There are practical limitations in the number of interconnections that can be implemented in order to make the design useful and operable. At the same time, by serializing a large number of data and control lines can result in a loss of timeliness of the data. The use of copper wire for the transmission of these signals has disadvantages such as added weight and bulk to the cable harness to the print head and because of electrical effects such as cable capacitance, crosstalk, and propagation delays (associated with long cable lengths). These design constraints make transmission of print head data by way of copper wire less attractive than by using a fiber optic transmission technique.
Prior art U.S. Pat. Nos. 5,396,078 and U.S. Pat. No. 6,357,859 describe the use of fiber optic data transmission for a printer. However, the prior art does not apply the technique of multiplexing to the fiber optic data channel to maximize the use of the wide bandwidth available with fiber optic transmission techniques to replace a number of electrical signals transmitted over copper wire. Also, this prior art describes a printer design where the print head carriage assembly does not contain the controller but discloses instead that the controller is located remotely to the print head and linked to the printhead by way of the fiber optic link.
U.S. Pat. No. 5,676,475 describes a printing system where the controller is located with the print head on the printer carriage. This implementation involves data rates of around 160 Kbytes per second and bursts of data up to 2 Mbytes per second. Also, this prior art describes a typical printer as containing 200 firing jets or nozzles. This implementation also utilizes a fiber optic data link. The data link is positioned such that it brings externally generated printer data to the controller, which is located with the print head at the printer carriage. No use of multiplexing is disclosed in the description of the fiber optic interface shown.
It is desirable, particularly in high speed industrial printing applications such as (1) the printing of wallpaper, the printing of photographs as examples of a drum or web type printing machinery or (2) for the printing of corrugated, packaging material, printing plates (flexographic or lithographic), or other media that necessitates the use of a flatbed type platen with an overhead x-y positionable carriage with print heads, that the quantity of electronic circuitry be minimized as much as possible that is packaged upon the carriage. The location of a controller or print engine on the carriage (1) adds significant circuitry that includes microprocessor clocks and circuits that contribute potential electrical interference and (2) may require special protection from inkjet fluids, such as conformal coating and (3) they and their power supply circuits add to the weight borne by the carriage, thus adding cost and complexity to the mechanical design and (3) these additional circuits add bulk and weight to the power cable assembly linking the carriage to the main section of the printing machinery. Thus it is desirable in high speed and/or large inkjet printing array assemblies to minimize the quantity of electronic circuits located on the print head carriage.
Accordingly, a printer assembly utilizing the fiber optic transmission method with multiplexing of the data provides advantages over prior art methods of transmitting data to the print heads where the controller is remotely located from the print head